The purpose of this laboratory is to explore the molecular mechanisms that determine the RNA replication process of HCV and of the HCV-related pestivirus BVDV. Previously, we identified and characterized the HCV RNA polymerase and developed a tissue culture system for BDV replication that we used to identify signals on viral RNA controlling translation and replication. Building on our expertise with BVDV, the scope of this application is to investigate the viral and cellular determinants that orchestrate the replication of the HCV genome. Comprehensive reverse genetic and biochemical studies will be performed to determine the functions of the viral proteins and RNA elements as well as a set of recently identified host proteins required for HCV replication. The hepatitis C virus (HCV) endemic affects more than 170 million people which are at risk for the development of severe liver disease including fibrosis, cirrhosis and hepatocullular carcinoma. The characterization of viral and cellular factors that play a role in the HCV life cycle is expected to lead to a better understanding of the mechanism responsible for the persistence of the virus in infected patients. In addition, it will reveal novel targets that can be used for the future development of effective antiviral drugs.